Recent tests have shown that, in internal combustion engines, in particular gasoline or Otto-cycle engines, a significant fraction of the exhaust-gas particles generated and emitted by such engines arises from oil contained in the intake air, for example in the form of oil droplets or oil vapors. The amounts of oil contained in the intake air are caused by leakage losses from components arranged in or connected to the intake tract of the internal combustion engine, such as for example a turbocharger or crankcase ventilation or inlet valve arrangements. The oil in the intake air may easily lead to a particle emissions level close to the limit values of future exhaust-gas standards. To adhere to said exhaust-gas standards, it is therefore desirable to reduce the oil content in the intake air as far as possible in order to be able to dispense with the use of expensive particle filter units in the exhaust-gas tract of the internal combustion engine.
It is known that, during the cooling of the air or of the air mixture in the charge-air-cooler, moisture (e.g. water) can condense out of the intake air. Additionally, the moisture can be discharged from the charge-air-cooler after being condensed out.
For example, U.S. Pat. No. 8,061,135 discloses a condensate discharge arrangement for discharging condensate from the interior of a charge-air-cooler of a turbocharger arrangement for an internal combustion engine. A first end of a hose element is connected in fluid-conducting fashion to a downstream end of the charge-air-cooler, the second end of which hose element is connected in fluid-conducting fashion directly, bypassing a throttle flap, to an intake manifold of the internal combustion engine. The hose element removes condensate from the charge-air-cooler continuously in reaction to a pressure gradient generated by the throttle flap when the internal combustion engine is in an activated state.
The inventors herein have recognized the above issues as well as issues with approaches such as described in U.S. Pat. No. 8,061,135. For example, a vessel for collecting the condensate, specifically oil droplets, at the charge-air-cooler is not present. Further, the use of a hose element to remove condensate may consume engine space.
In one example, some of the above issues may be addressed by a method for discharging liquid from an intake tract of a turbocharger arrangement comprising, collecting the liquid in a liquid collector including a liquid outlet. As such, the liquid outlet may be closed off by a switchable valve downstream of the charge-air-cooler. The switchable valve may be adjusted following the determination of an opening frequency and an opening duration based on a liquid collector temperature and a liquid collector pressure. In this way, the technical effect is achieved that oil may be reliably discharged from an intake tract of a turbocharger arrangement, thereby decreasing emissions from a vehicle.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.